Synthesis and spectroscopic characterization of tin(II) and tin(IV) complexes containing 2,3,5,6-tetrakis(alpha-pyridyl)pyrazine as a bridging ligand

In this work we investigated the reactivity of the nitrogen heterocyclic ligand 2,3,5,6-tetrakis(alpha-pyridyl)pyrazine, TPP, towards six tin-containing reagents, namely SnCl2, SnX4 (X = Cl or Br), SnRCl3 (R = Ph or Me), and SnPh2Cl2. The products were characterized by microanalysis (C, H, N, and Sn), IR spectroscopy (4000-200 cm-1), ¹H, 13C{¹H}, 13C-CP/MAS, 119Sn, and 119Sn-MAS NMR spectroscopy, as well as by 119Sn Mössbauer spectroscopy. All reactions yielded bimetallic adducts, in which TPP behaved as a bis-bidentate bridging ligand, binding to each metallic center through two pyridine nitrogen atoms. This coordination mode is so far quite rare and, for the first time, is reported for main group metal-TPP complexes.